I. ( a− )⋅(2a+ )=4a2−16b2
2a⋅2a+ a⋅ − ⋅2a− ⋅ =4a2−16b2
2a⋅2a+2a⋅ − ⋅2a−4b⋅4b=4a2−16b2 2a⋅2a+2a⋅ − ⋅2a−4b⋅4b=4a2−16b2
2a⋅2a+2a⋅4b−4b⋅2a−4b⋅4b=4a2−16b2
(2a−4b)(2a+4b)=4a2−16b2
Zauwaz˙amy wzoˊr skroˊconego mnoz˙enia i rozwiązujemy kolejne podpunkty w oparciu o znajomosˊcˊ tej zalez˙nosˊci:
(x−y)(x−y)=x2−y2
II. ( −31b)⋅(32a+ )= a2−91b2
(32a−31b)⋅(32a+31b)=(32)2a2−91b2
(32a−31b)⋅(32a+31b)=94a2−91b2
III. 0,36a2−0,04b2=(0,6a− )⋅( a+ )
0,36a2−0,04b2=(0,6a−0,2b)⋅(0,6a+0,2b)